DiGeorge syndrome
Encyclopedia
22q11.2 deletion syndrome, which has several presentations including DiGeorge syndrome (DGS), DiGeorge anomaly, velo-cardio-facial syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, Strong syndrome, congenital thymic aplasia, and thymic hypoplasia is a syndrome caused by the deletion of a small piece of chromosome 22
. The deletion occurs near the middle of the chromosome
at a location designated q11.2 i.e., on the long arm of one of the pair of chromosomes 22, on region 1, band 1 , sub-band 2. It has a prevalence estimated at 1:4000. The syndrome was described in 1968 by the pediatric endocrinologist Angelo DiGeorge
.
, mild differences in facial features, and recurrent infection
s. Infections are common in children due to problems with the immune system
's T-cell mediated response that in some patients is due to an absent or hypoplastic thymus
. 22q11.2 deletion syndrome may be first spotted when an affected newborn has heart defects or convulsions from hypocalcemia due to malfunctioning parathyroid glands and low levels of parathyroid hormone (parathormone). Affected individuals may also have any other kind of birth defect including kidney abnormalities and significant feeding difficulties as babies. Autoimmune disorders such as hypothyroidism
and hypoparathyroidism
or thrombocytopenia
(low platelet levels), and psychiatric illnesses are common late-occurring features. Microdeletions in chromosomal region 22q11.2 are associated with a 20 to 30-fold increased risk of schizophrenia
.
Studies provide various rates of 22q11.2 deletion syndrome in schizophrenia, ranging from 0.5 to 2% and averaging about 1%, compared with the overall estimated 0.025% risk of the 22q11.2 deletion syndrome in the general population.
Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge's syndrome, with the 22 to remind one the chromosomal abnormality is found on the 22 chromosome, as below:
Cardiac Abnormality (especially tetralogy of Fallot
)
Abnormal facies
Thymic aplasia
Cleft palate
Hypocalcemia.
The mechanism that causes all of the associated features of the syndrome is unknown. 22q11.2 deletion syndrome may involve migration defects of neural crest
-derived tissues, particularly affecting development of the third and fourth branchial pouches (pharyngeal pouches). This affects the thymus gland; a mediastinal organ largely responsible for differentiation and induction of tolerance in T-cells, and the Parathyroid glands, responsible for regulation of blood calcium levels.
For example, in children it is important that the immune problems are identified early as special precautions are required regarding blood transfusion and immunisation with live vaccines. Thymus
transplantation
can be used to address absence of the thymus in the rare, so-called "complete" DiGeorge syndrome. Bacterial infections are treated with antibiotics. Cardiac surgery
is often required for congenital heart abnormalities. Hypoparathyroidism causing hypocalcaemia often requires lifelong vitamin D and calcium supplements.
22 detected by fluorescence in situ hybridization (FISH) or BACs-on-Beads technology. In FISH one DNA probes from the 22q11.2 chromosomal region is used at a time, while with BACs-on-Beads technology multiple probes from the 22q11.2 region can be used simultaneously. Such genetic testing
is widely available for the clinical and prenatal testing of the 22q11.2 deletion syndrome. Fewer than 5% of individuals with clinical symptoms of the 22q11.2 deletion syndrome have normal routine cytogenetic studies and negative FISH testing. Some cases of DiGeorge Syndrome have defects in other chromosomes, notably a deletion in chromosome region 10p14. They may have variant deletions of DiGeorge syndrome that may be detectable on a research basis only or with other more advanced clinical testing method.
Most people with 22q11.2 deletion syndrome are missing about 3 million base pair
s on one copy of chromosome 22
in every cell of their body. This region contains about 45 genes, but some of these genes have not been well characterized. A small percentage of affected individuals have shorter deletions in the same region.
Researchers have not yet identified the genes that contribute to the features of 22q11.2 deletion syndrome. They have determined that the loss of one particular gene on chromosome 22, TBX1
, is probably responsible for some of the syndrome's characteristic signs (such as heart defects). Carrying only one copy of this gene does not appear to cause learning disabilities, however. Additional genes in the deleted region are likely to contribute to the signs and symptoms of 22q11.2 deletion syndrome and genes outside the 22q11.2 region may also play a role.
The 22q11.2 deletion syndrome can be inherited, but this is the case in the minority of newly diagnosed individuals. Only 5–10% have inherited the 22q11.2 deletion from a parent, whereas about 90–95% of cases have a de novo (new to the family) deletion of 22q11.2. This is because the 22q11.2 region has a structure that makes it highly prone to rearrangements during sperm or egg formation. The deletion is almost equally likely to occur when an egg is formed as when a sperm is formed. An individual with deletion 22q11.2 has a 50% (one in two) chance of passing the 22q11.2 deletion to their offspring. Prenatal testing, such as amniocentesis
, is available for pregnancies determined to be at risk. Also, pregnancies with findings of congenital heart disease and/or palate anomalies detected by ultrasound examination may be offered prenatal testing for 22q11.2 deletion syndrome. Because most of the signs of this cluster of defects can also be inherited as autosomal recessive or x-linked traits, only genetic testing of both parents can determine with any certainty the likelihood of these anomalies occurring in any subsequent children.
It is one of the most common causes of mental retardation
due to a genetic deletion syndrome.
Noteworthy is that these patients are a specifically high-risk group for developing schizophrenia. 30% have at least one incident of psychosis
and about a quarter develop actual schizophrenia
.
Hypernasality occurs when air escapes through the nose during the production of oral speech sounds resulting in reduced intelligibility
. This is a common characteristic in the speech and language profile because 69% of children have palatal abnormalities. If the structure of the soft palate velum
is such that it does not stop the flow of air from going up to the nasal cavity
, it will cause hypernasal speech
. This phenomenon is referred as velopharyngeal inadequacy
VPI. Hearing loss can also contribute to increased hypernasality because children with hearing impairments can have difficulty self monitoring their oral speech output. The treatment options available for VPI include prosthesis and surgery.
Difficulties acquiring vocabulary and formulating spoken language (expressive language deficits) at the onset of language development are also part of the speech and language profile associated with the 22q11.2 deletion. Vocabulary acquisition is often severely delayed for preschool age children. In some recent studies, children had a severely limited vocabulary or were still nonverbal at 2–3 years of age. School age children do make progress with expressive language as they mature, but many continue to have delays and demonstrate difficulty when presented with language tasks such as verbally recalling narratives and producing longer and more complex sentences. Receptive language, which is the ability to comprehend, retain, or process spoken language, can also be impaired although not usually with the same severity as expressive language impairments.
Articulation
errors are commonly present in children with 22q11.2 deletion syndrome. These errors include a limited phonemic (speech sound) inventory and the use of compensatory articulation strategies resulting in reduced intelligibility. The phonemic inventory typically produced consists of sounds made in the front or back of the vocal tract such as: /p/, /w/, /j/, /m/, /n/, and glottal stops. Mid vocal tract sounds are completely absent. Compensatory articulation errors made by this population of children include: glottal stop
s, nasal substitutions, pharyngeal fricatives, linguapalatal sibilants, reduced pressure on consonant sounds, or a combination of these symptoms. Of these errors, glottal stops have the highest frequency of occurrence. It is reasoned that a limited phonemic inventory and the use of compensatory articulation strategies is present due to the structural abnormalities of the palate. The speech impairments exhibited by this population are more severe during the younger ages and show a trend of gradual improvement as the child matures.
Chromosome 22 (human)
Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of Chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and representing between 1.5 and 2 % of the total DNA in cells.In 1999,...
. The deletion occurs near the middle of the chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
at a location designated q11.2 i.e., on the long arm of one of the pair of chromosomes 22, on region 1, band 1 , sub-band 2. It has a prevalence estimated at 1:4000. The syndrome was described in 1968 by the pediatric endocrinologist Angelo DiGeorge
Angelo DiGeorge
Angelo M. DiGeorge was an Italian American physician and pediatric endocrinologist who is renowned for his research on an autosomal dominant immunodeficiency now commonly referred to as DiGeorge syndrome....
.
Presentation
The features of this syndrome vary widely, even among members of the same family, and affect many parts of the body. Characteristic signs and symptoms may include birth defects such as congenital heart disease, defects in the palate, most commonly related to neuromuscular problems with closure (velo-pharyngeal insufficiency), learning disabilitiesLearning disability
Learning disability is a classification including several disorders in which a person has difficulty learning in a typical manner, usually caused by an unknown factor or factors...
, mild differences in facial features, and recurrent infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s. Infections are common in children due to problems with the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
's T-cell mediated response that in some patients is due to an absent or hypoplastic thymus
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
. 22q11.2 deletion syndrome may be first spotted when an affected newborn has heart defects or convulsions from hypocalcemia due to malfunctioning parathyroid glands and low levels of parathyroid hormone (parathormone). Affected individuals may also have any other kind of birth defect including kidney abnormalities and significant feeding difficulties as babies. Autoimmune disorders such as hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
and hypoparathyroidism
Hypoparathyroidism
Hypoparathyroidism is decreased function of the parathyroid glands with under production of parathyroid hormone. This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany , and several other symptoms...
or thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
(low platelet levels), and psychiatric illnesses are common late-occurring features. Microdeletions in chromosomal region 22q11.2 are associated with a 20 to 30-fold increased risk of schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
.
Studies provide various rates of 22q11.2 deletion syndrome in schizophrenia, ranging from 0.5 to 2% and averaging about 1%, compared with the overall estimated 0.025% risk of the 22q11.2 deletion syndrome in the general population.
Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge's syndrome, with the 22 to remind one the chromosomal abnormality is found on the 22 chromosome, as below:
Cardiac Abnormality (especially tetralogy of Fallot
Tetralogy of Fallot
Tetralogy of Fallot is a congenital heart defect which is classically understood to involve four anatomical abnormalities...
)
Abnormal facies
Facies (medical)
In medical contexts, facies are distinctive facial expressions associated with specific medical conditions.It comes from the Latin word for "face".As a fifth declension noun, "facies" can refer to the singular or plural.-Types:Examples include:...
Thymic aplasia
Cleft palate
Hypocalcemia.
Nomenclature
The signs and symptoms of 22q11 deletion syndrome are so varied that different groupings of its features were once regarded as separate conditions. These original classifications included velo-cardio-facial syndrome, Shprintzen syndrome, DiGeorge sequence/syndrome, Sedlackova syndrome and conotruncal anomaly face syndrome. All are now understood to be presentations of a single syndrome.Symptoms
Individuals with a 22q11.2 deletion can suffer from many possible features, ranging in number of associated features and from the mild to the very serious. Symptoms shown to be common include:- Congenital heart disease (40% of individuals), particularly conotruncalBulbus cordisThe bulbus cordis lies ventral to the primitive ventricle after the developing heart assumes its S-shaped form...
malformations (tetralogy of FallotTetralogy of FallotTetralogy of Fallot is a congenital heart defect which is classically understood to involve four anatomical abnormalities...
, interrupted aortic archInterrupted aortic archInterrupted aortic arch is a very rare heart defect in which the aorta is not completely developed. There is a gap between the ascending and descending thoracic aorta. Almost all patients also have other cardiac anomalies. Interrupted aortic arch is often associated with DiGeorge...
, ventricular septal defectVentricular septal defectA ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
, and persistent truncus arteriosusPersistent truncus arteriosusPersistent truncus arteriosus , also known as Common arterial trunk, is a rare form of congenital heart disease that presents at birth...
) - palatal abnormalities (50%), particularly velopharyngeal incompetence (VPI), submucosal cleft palate, and cleft palate; characteristic facial features (present in the majority of CaucasianCaucasian raceThe term Caucasian race has been used to denote the general physical type of some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia , Central Asia and South Asia...
individuals) including hypertelorismHypertelorismHypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits . In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal...
. - learning difficulties (90%) but broad range
- hypocalcemia (50%)(due to hypoparathyroidism)
- significant feeding problems (30%)
- renal anomalies (37%)
- hearing lossHearing impairment-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
(both conductive and sensorineural) (Hearing loss with craniofacial syndromesHearing loss with craniofacial syndromesHearing loss with craniofacial syndromes is a common occurrence. Many of these multianomaly disorders involve structural malformations of the outer or middle ear, making a significant hearing loss highly likely.- Treacher Collins syndrome :...
) - laryngotracheoesophageal anomalies
- growth hormoneGrowth hormoneGrowth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior...
deficiency - autoimmune disorders
- seizures (without hypocalcemia)
- skeletal abnormalities
- psychiatric disorders
Cause
The syndrome is caused by genetic deletions (loss of a small part of the genetic material) found on the long arm of one of the two 22nd chromosomes. Very rarely, patients with somewhat similar clinical features may have deletions on the short arm of chromosome 10.The mechanism that causes all of the associated features of the syndrome is unknown. 22q11.2 deletion syndrome may involve migration defects of neural crest
Neural crest
Neural crest cells are a transient, multipotent, migratory cell population unique to vertebrates that gives rise to a diverse cell lineage including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia....
-derived tissues, particularly affecting development of the third and fourth branchial pouches (pharyngeal pouches). This affects the thymus gland; a mediastinal organ largely responsible for differentiation and induction of tolerance in T-cells, and the Parathyroid glands, responsible for regulation of blood calcium levels.
Treatment
There is no cure for 22q11.2 deletion syndrome. Certain individual features are treatable using standard treatments. The key is to identify each of the associated features and manage each using the best available treatments.For example, in children it is important that the immune problems are identified early as special precautions are required regarding blood transfusion and immunisation with live vaccines. Thymus
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
transplantation
Organ transplant
Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...
can be used to address absence of the thymus in the rare, so-called "complete" DiGeorge syndrome. Bacterial infections are treated with antibiotics. Cardiac surgery
Cardiac surgery
Cardiovascular surgery is surgery on the heart or great vessels performed by cardiac surgeons. Frequently, it is done to treat complications of ischemic heart disease , correct congenital heart disease, or treat valvular heart disease from various causes including endocarditis, rheumatic heart...
is often required for congenital heart abnormalities. Hypoparathyroidism causing hypocalcaemia often requires lifelong vitamin D and calcium supplements.
Diagnosis and testing
The 22q11.2 deletion syndrome is diagnosed in individuals with a submicroscopic deletion of chromosomeChromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
22 detected by fluorescence in situ hybridization (FISH) or BACs-on-Beads technology. In FISH one DNA probes from the 22q11.2 chromosomal region is used at a time, while with BACs-on-Beads technology multiple probes from the 22q11.2 region can be used simultaneously. Such genetic testing
Genetic testing
Genetic testing is among the newest and most sophisticated of techniques used to test for genetic disorders which involves direct examination of the DNA molecule itself. Other genetic tests include biochemical tests for such gene products as enzymes and other proteins and for microscopic...
is widely available for the clinical and prenatal testing of the 22q11.2 deletion syndrome. Fewer than 5% of individuals with clinical symptoms of the 22q11.2 deletion syndrome have normal routine cytogenetic studies and negative FISH testing. Some cases of DiGeorge Syndrome have defects in other chromosomes, notably a deletion in chromosome region 10p14. They may have variant deletions of DiGeorge syndrome that may be detectable on a research basis only or with other more advanced clinical testing method.
Genetics
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
s on one copy of chromosome 22
Chromosome 22 (human)
Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of Chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and representing between 1.5 and 2 % of the total DNA in cells.In 1999,...
in every cell of their body. This region contains about 45 genes, but some of these genes have not been well characterized. A small percentage of affected individuals have shorter deletions in the same region.
Researchers have not yet identified the genes that contribute to the features of 22q11.2 deletion syndrome. They have determined that the loss of one particular gene on chromosome 22, TBX1
TBX1
TBX1 is a human gene that codes for the protein called T-box 1. Genes in the T-box family play important roles in the formation of tissues and organs during embryonic development. To carry out these roles, proteins made by this gene family bind to specific areas of DNA. By attaching to critical...
, is probably responsible for some of the syndrome's characteristic signs (such as heart defects). Carrying only one copy of this gene does not appear to cause learning disabilities, however. Additional genes in the deleted region are likely to contribute to the signs and symptoms of 22q11.2 deletion syndrome and genes outside the 22q11.2 region may also play a role.
The 22q11.2 deletion syndrome can be inherited, but this is the case in the minority of newly diagnosed individuals. Only 5–10% have inherited the 22q11.2 deletion from a parent, whereas about 90–95% of cases have a de novo (new to the family) deletion of 22q11.2. This is because the 22q11.2 region has a structure that makes it highly prone to rearrangements during sperm or egg formation. The deletion is almost equally likely to occur when an egg is formed as when a sperm is formed. An individual with deletion 22q11.2 has a 50% (one in two) chance of passing the 22q11.2 deletion to their offspring. Prenatal testing, such as amniocentesis
Amniocentesis
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
, is available for pregnancies determined to be at risk. Also, pregnancies with findings of congenital heart disease and/or palate anomalies detected by ultrasound examination may be offered prenatal testing for 22q11.2 deletion syndrome. Because most of the signs of this cluster of defects can also be inherited as autosomal recessive or x-linked traits, only genetic testing of both parents can determine with any certainty the likelihood of these anomalies occurring in any subsequent children.
Epidemiology
22q11.2 deletion syndrome affects between 1 in 2000 and 1 in 4000 live births. This estimate is based on major birth defects and may be an underestimate, because some individuals with the deletion have few symptoms and may not have been formally diagnosed.It is one of the most common causes of mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
due to a genetic deletion syndrome.
Cognitive impairments
Children with 22q11.2 have a specific profile in neuropsychological tests. They usually have a borderline normal IQ with most individuals having higher scores in the verbal than the nonverbal domains. Cognitive functioning when processing information involving space and time usually shows significant impairment and this generally slows the development of numerical and arithmetical knowledge and skills.Noteworthy is that these patients are a specifically high-risk group for developing schizophrenia. 30% have at least one incident of psychosis
Psychosis
Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...
and about a quarter develop actual schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
.
Speech and language
Current research demonstrates there is a unique profile of speech and language impairments associated with 22q11.2 deletion syndrome. Children often perform lower on speech and language evaluations in comparison to their nonverbal IQ scores. Common problems include hypernasality, language delays, and speech sound errors.Hypernasality occurs when air escapes through the nose during the production of oral speech sounds resulting in reduced intelligibility
Intelligibility
In phonetics, Intelligibility is a measure of how comprehendible speech is, or the degree to which speech can be understood. Intelligibility is affected by spoken clarity, explicitness, lucidity, comprehensibility, perspicuity, and precision.-Noise levels:...
. This is a common characteristic in the speech and language profile because 69% of children have palatal abnormalities. If the structure of the soft palate velum
Soft palate
The soft palate is the soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone....
is such that it does not stop the flow of air from going up to the nasal cavity
Nasal cavity
The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
, it will cause hypernasal speech
Hypernasal speech
Rhinolalia , aperta = open, is the medical term for hypernasal speech. The other terms are hyperrhinolalia and open nasality. Hypernasality is a disorder of nasal speech when the sound of the voice is different, an abnormal resonance...
. This phenomenon is referred as velopharyngeal inadequacy
Velopharyngeal inadequacy
Velopharyngeal inadequacy is a malfunction of a velopharyngeal mechanism.The velopharyngeal mechanism is responsible for directing the transmission of sound energy and air pressure in both the oral cavity and the nasal cavity. When this mechanism is impaired in some way, the valve does not fully...
VPI. Hearing loss can also contribute to increased hypernasality because children with hearing impairments can have difficulty self monitoring their oral speech output. The treatment options available for VPI include prosthesis and surgery.
Difficulties acquiring vocabulary and formulating spoken language (expressive language deficits) at the onset of language development are also part of the speech and language profile associated with the 22q11.2 deletion. Vocabulary acquisition is often severely delayed for preschool age children. In some recent studies, children had a severely limited vocabulary or were still nonverbal at 2–3 years of age. School age children do make progress with expressive language as they mature, but many continue to have delays and demonstrate difficulty when presented with language tasks such as verbally recalling narratives and producing longer and more complex sentences. Receptive language, which is the ability to comprehend, retain, or process spoken language, can also be impaired although not usually with the same severity as expressive language impairments.
Articulation
Articulation
Articulation may refer to:In linguistics:* Topic–focus articulation, a field of study concerned with marking old and new information in a clause* Manner of articulation, how speech organs involved in making a sound make contact...
errors are commonly present in children with 22q11.2 deletion syndrome. These errors include a limited phonemic (speech sound) inventory and the use of compensatory articulation strategies resulting in reduced intelligibility. The phonemic inventory typically produced consists of sounds made in the front or back of the vocal tract such as: /p/, /w/, /j/, /m/, /n/, and glottal stops. Mid vocal tract sounds are completely absent. Compensatory articulation errors made by this population of children include: glottal stop
Glottal stop
The glottal stop, or more fully, the voiceless glottal plosive, is a type of consonantal sound used in many spoken languages. In English, the feature is represented, for example, by the hyphen in uh-oh! and by the apostrophe or [[ʻokina]] in Hawaii among those using a preservative pronunciation of...
s, nasal substitutions, pharyngeal fricatives, linguapalatal sibilants, reduced pressure on consonant sounds, or a combination of these symptoms. Of these errors, glottal stops have the highest frequency of occurrence. It is reasoned that a limited phonemic inventory and the use of compensatory articulation strategies is present due to the structural abnormalities of the palate. The speech impairments exhibited by this population are more severe during the younger ages and show a trend of gradual improvement as the child matures.